A neutron diffraction and Mössbauer study of NdFe9.25Si1.75Cx compounds

Abstract The crystallographic structures, magnetic properties and hyperfine interactions of NdFe 9.25 Si 1.75 C x have been studied using neutron diffraction, magnetic and 57 Fe Mossbauer spectra measurements. The refinement of the powder neutron diffraction demonstrates that NdFe 9.25 Si 1.75 C 1.5 crystallizes in the BaCd 11 -type structure with space group I4 1 /amd and four formula units per unit cell. Nd atoms occupy 4a sites, and Fe atoms distribute on 4b, 8d and 32i sites. Si and C atoms occupy 8d and 8c sites, respectively. The saturation magnetization, the isomer shift (IS) and the hyperfine field reach their highest values at the carbon content x =1.0. With a set of phenomenological formulas, the contribution of the magneto-volume effect and the chemical bonding effect to the hyperfine parameters are successfully separated. The pure magneto-volume effect and the pure chemical bonding effect influence the hyperfine field and the IS differently. The former one increases both of them and the latter one decreases them. This is consistent with the rather strong bond between Fe(32i) and C(8c).